The conditions for opening the Purgatory Gate Trial Ground are extremely stringent. The entire gate has seventy-two slots, meaning seventy-two gemstones are needed to open the Trial Gate, which is a much higher requirement than the average Trial Gate.
A standard Trial Gate can be opened with more than ten gemstones, and the Sea Heaven Trial Ground needs thirty-six gemstones. The Purgatory Gate needs seventy-two, which is twice that of the Sea Heaven Trial Ground.
Even more terrifying is that Red Sand City researched for a long time, initially trying various gemstones, but couldn't open the Purgatory Gate. Until someone suddenly had a flash of inspiration, embedding thirty-six blue gemstones and thirty-six rubies into the Purgatory Gate, which then lit up, showing signs of opening.
